Nitrogen-oxygen bonds, hydrogenolysis

Both benzyl-oxygen and nitrogen-oxygen bonds undergo hydrogenolysis readily in the presence of a benzyloxy-nitrogen bond but it appears that the benzyl-oxygen bond can be made to cleave selec-... 

The nitrogen-oxygen bond is usually cleaved readily by catalytic hydrogenolysis and the reaction has wide synthetic utility. 

Pre-treatment of the cathode produces a finely divided copper surface and this catalyses the hydrogenolysis of phenylhydroxylamine to aniline which becomes the principal reaction product. The reaction probably involves promotion of nitrogen-oxygen bond cleavage in the chemisorbed phenylhydroxylamine intermediate. 

Benzyl-nitrogen, sulfur, or -oxygen bonds are somewhat susceptible to hydrogenolysis, either during catalytic hydrogenation (30, 31), or upon treatment with L-selectride (32), or even lithium aluminium hydride (33). 

It is widely accepted that a benzyl-nitrogen bond is not as readily cleaved as a benzyl-oxygen bond. The presence of nitrogen can, however, influence the hydrogenolysis of C-O bonds. It has been reported that butylamine completely prevented the hydrogenolysis of the benzylic C-O bond [62]. The same effect was observed for molecules containing both benzylic C-O and C-N bonds [62,63]. In a mixture of A-benzylcyclohexylamine and benzyl cyclohexyl ether only the C-N bond was hydrogenolyzed on Pd/C, whereas in the presence of HCl the... 

The same was found for nitrogen-containing compounds protected by benzyl-oxymethyl groups. These compounds have two reactive bonds. The regioselectivity of the hydrogenolysis depends on the catalyst used. The carbon-oxygen bond was ruptured by use of Pd/C as catalyst whereas the rupture of the C-N bond occurred when hydrogenolysis was performed with Pd(OH)2 in MeOH (Scheme 8) [65]. 

Hydrogenolysis is analogous to hydrolysis and ammonolysis, which involve the cleavage of a bond induced by the action of water and ammonia, respectively. Chemical bonds that are broken by hydrogenolysis reactions include carbon—carbon, carbon—oxygen, carbon—sulfur, and carbon—nitrogen bonds. An example of hydrogenolysis is the hydrodealkylation of toluene to form benzene and methane ... 

Both benzyl-oxygen and N-O bonds can undergo hydrogenolysis in the compounds containing benzyloxy-nitrogen bonds,... 

---